London: Any books that cover 1.d4 d5 2.Nf3 Bg4 well?

The best book is a data base. Here is a game:

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I remember this game: ... f6 was somehow shocking at the time!

@4

No it is not shocking: after 1 d4 Nf6 2 Bg5 Ne4 3 Bf4 white plays 4 f3 too.

You could play 2. Bf4 instead of 2.Nf3 to get into London

The opening sequence 1.Nf3 d5 2.d4 Bg4 was played in the 1889 World Championship match (game 14) between Steinitz and Chigorin. The game is classified as "Queen's Gambit Declined: Chigorin Defense". Although the game was analyzed in a book on the London System, since it does not contain the move Bf4 by White, it isn't technically a 'London System' opening. I included the game here because it features the first 4 moves specified by the OP...

https://www.chessgames.com/perl/chessgame?gid=1036314

The game is analyzed in detail in "First Steps; the Colle and London Systems" by Cyrus Lakdawala, Everyman Chess, 2016, pp.71-77.

However, the opening sequence 1.Nf3 d5 2.d4 Nc6 3.Bf4 Bg4 was played in the game Ian Rogers - Ye Rongguan, Kuala Lumpur, 1990 and is analyzed in detail in "Win With the London System" by Johnsen and Kovacevic, Gambit Publications, 2005, pp. 31-33. The authors refer to it as the "Chigorin Setup".

https://www.chessgames.com/perl/chessgame?gid=1117389

@7
The Chigorin Defense is characterised by 3...Nc6. There are alternatives: 3...c6 or 3...e6.

Finally, a game (Eduardas Rozentalis - Jakub Zeberski 2007) with the opening sequence 1.d4 d5 2.Nf3 Nc6 3.Bf4 Bg4 is analyzed in detail in Nicola Sedlak's first book (Part 1) on the London System, "Winning With The Modern London System", Chess Evolution, pp.203-209. The author refers to the opening as a 'Chigorin Setup'.

After a lengthy internet search, the only place I was able to find the game referenced along with a PGN was here...

https://ratings.fide.com/view_games.phtml?event=&id=1113020&opp=12800023

Only after 3...c5. After 3...d5 white plays 4.e3 and Bd3, f3 does not make much sense.

Thanks. Lakdawala it is then! Cheers. :)

@13

All listen to Uhohspaghettio1: he is rated 1030...